Seems like an open source project (funambol) has developed software that you can place on a Windows or Linux box with numerous clients including a BlackBerry client. The client will allow you to sync your contacts and calendar. It provides free push email for Windows Mobile devices too. You really need to check this one out. Here is the link: http://www.funambol.com/opensource/downloads.html
It appears that you can treat your PC as a server. Funambol Overview The world is mobile, but most people still don’t have email on their phones.
Over 750 million mobile phones and wireless devices were sold last year, and there will be more than a billion phones capable of wireless email this year. Yet most carriers offer mobile email only on expensive, proprietary devices. Why? Because up to now, there’s not been a standard way to get corporate email sent to low-cost phones.
Until now. The Open Mobile Alliance (OMA) has created a global standard protocol for sending and receiving email messages with “push” notification, plus synchronizing calendars, contact lists, and other PIM information. Most mobile phones support this standard for PIM today, and new phones are starting to support push email.
Funambol has created the first open source server that supports the latest OMA standards, so that you can provide email and PIM synchronization on low-cost wireless computing devices. The Funambol server connects to your existing email and calendar servers, providing two-way updates of messages and PIM data. Funambol client plug-ins provide OMA protocol support to the software that’s already embedded in your phones.